llvm-6502/lib/Target/X86/X86CodeEmitter.cpp

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//===-- X86/MachineCodeEmitter.cpp - Convert X86 code to machine code -----===//
//
// This file contains the pass that transforms the X86 machine instructions into
// actual executable machine code.
//
//===----------------------------------------------------------------------===//
#include "X86TargetMachine.h"
#include "X86.h"
#include "llvm/PassManager.h"
#include "llvm/CodeGen/MachineCodeEmitter.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/Value.h"
namespace {
class Emitter : public FunctionPass {
X86TargetMachine &TM;
const X86InstrInfo ⅈ
MachineCodeEmitter &MCE;
public:
Emitter(X86TargetMachine &tm, MachineCodeEmitter &mce)
: TM(tm), II(TM.getInstrInfo()), MCE(mce) {}
bool runOnFunction(Function &F);
private:
void emitBasicBlock(MachineBasicBlock &MBB);
void emitInstruction(MachineInstr &MI);
void emitRegModRMByte(unsigned ModRMReg, unsigned RegOpcodeField);
void emitSIBByte(unsigned SS, unsigned Index, unsigned Base);
void emitConstant(unsigned Val, unsigned Size);
void emitMemModRMByte(const MachineInstr &MI,
unsigned Op, unsigned RegOpcodeField);
};
}
/// addPassesToEmitMachineCode - Add passes to the specified pass manager to get
/// machine code emitted. This uses a MAchineCodeEmitter object to handle
/// actually outputting the machine code and resolving things like the address
/// of functions. This method should returns true if machine code emission is
/// not supported.
///
bool X86TargetMachine::addPassesToEmitMachineCode(PassManager &PM,
MachineCodeEmitter &MCE) {
PM.add(new Emitter(*this, MCE));
return false;
}
bool Emitter::runOnFunction(Function &F) {
MachineFunction &MF = MachineFunction::get(&F);
MCE.startFunction(MF);
for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)
emitBasicBlock(*I);
MCE.finishFunction(MF);
return false;
}
void Emitter::emitBasicBlock(MachineBasicBlock &MBB) {
MCE.startBasicBlock(MBB);
for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end(); I != E; ++I)
emitInstruction(**I);
}
namespace N86 { // Native X86 Register numbers...
enum {
EAX = 0, ECX = 1, EDX = 2, EBX = 3, ESP = 4, EBP = 5, ESI = 6, EDI = 7
};
}
// getX86RegNum - This function maps LLVM register identifiers to their X86
// specific numbering, which is used in various places encoding instructions.
//
static unsigned getX86RegNum(unsigned RegNo) {
switch(RegNo) {
case X86::EAX: case X86::AX: case X86::AL: return N86::EAX;
case X86::ECX: case X86::CX: case X86::CL: return N86::ECX;
case X86::EDX: case X86::DX: case X86::DL: return N86::EDX;
case X86::EBX: case X86::BX: case X86::BL: return N86::EBX;
case X86::ESP: case X86::SP: case X86::AH: return N86::ESP;
case X86::EBP: case X86::BP: case X86::CH: return N86::EBP;
case X86::ESI: case X86::SI: case X86::DH: return N86::ESI;
case X86::EDI: case X86::DI: case X86::BH: return N86::EDI;
default:
assert(RegNo >= MRegisterInfo::FirstVirtualRegister &&
"Unknown physical register!");
assert(0 && "Register allocator hasn't allocated reg correctly yet!");
return 0;
}
}
inline static unsigned char ModRMByte(unsigned Mod, unsigned RegOpcode,
unsigned RM) {
assert(Mod < 4 && RegOpcode < 8 && RM < 8 && "ModRM Fields out of range!");
return RM | (RegOpcode << 3) | (Mod << 6);
}
void Emitter::emitRegModRMByte(unsigned ModRMReg, unsigned RegOpcodeFld){
MCE.emitByte(ModRMByte(3, RegOpcodeFld, getX86RegNum(ModRMReg)));
}
void Emitter::emitSIBByte(unsigned SS, unsigned Index, unsigned Base) {
// SIB byte is in the same format as the ModRMByte...
MCE.emitByte(ModRMByte(SS, Index, Base));
}
void Emitter::emitConstant(unsigned Val, unsigned Size) {
// Output the constant in little endian byte order...
for (unsigned i = 0; i != Size; ++i) {
MCE.emitByte(Val & 255);
Val >>= 8;
}
}
static bool isDisp8(int Value) {
return Value == (signed char)Value;
}
void Emitter::emitMemModRMByte(const MachineInstr &MI,
unsigned Op, unsigned RegOpcodeField) {
const MachineOperand &BaseReg = MI.getOperand(Op);
const MachineOperand &Scale = MI.getOperand(Op+1);
const MachineOperand &IndexReg = MI.getOperand(Op+2);
const MachineOperand &Disp = MI.getOperand(Op+3);
// Is a SIB byte needed?
if (IndexReg.getReg() == 0 && BaseReg.getReg() != X86::ESP) {
if (BaseReg.getReg() == 0) { // Just a displacement?
// Emit special case [disp32] encoding
MCE.emitByte(ModRMByte(0, RegOpcodeField, 5));
emitConstant(Disp.getImmedValue(), 4);
} else {
unsigned BaseRegNo = getX86RegNum(BaseReg.getReg());
if (Disp.getImmedValue() == 0 && BaseRegNo != N86::EBP) {
// Emit simple indirect register encoding... [EAX] f.e.
MCE.emitByte(ModRMByte(0, RegOpcodeField, BaseRegNo));
} else if (isDisp8(Disp.getImmedValue())) {
// Emit the disp8 encoding... [REG+disp8]
MCE.emitByte(ModRMByte(1, RegOpcodeField, BaseRegNo));
emitConstant(Disp.getImmedValue(), 1);
} else {
// Emit the most general non-SIB encoding: [REG+disp32]
MCE.emitByte(ModRMByte(2, RegOpcodeField, BaseRegNo));
emitConstant(Disp.getImmedValue(), 4);
}
}
} else { // We need a SIB byte, so start by outputting the ModR/M byte first
assert(IndexReg.getReg() != X86::ESP && "Cannot use ESP as index reg!");
bool ForceDisp32 = false;
bool ForceDisp8 = false;
if (BaseReg.getReg() == 0) {
// If there is no base register, we emit the special case SIB byte with
// MOD=0, BASE=5, to JUST get the index, scale, and displacement.
MCE.emitByte(ModRMByte(0, RegOpcodeField, 4));
ForceDisp32 = true;
} else if (Disp.getImmedValue() == 0 && BaseReg.getReg() != X86::EBP) {
// Emit no displacement ModR/M byte
MCE.emitByte(ModRMByte(0, RegOpcodeField, 4));
} else if (isDisp8(Disp.getImmedValue())) {
// Emit the disp8 encoding...
MCE.emitByte(ModRMByte(1, RegOpcodeField, 4));
ForceDisp8 = true; // Make sure to force 8 bit disp if Base=EBP
} else {
// Emit the normal disp32 encoding...
MCE.emitByte(ModRMByte(2, RegOpcodeField, 4));
}
// Calculate what the SS field value should be...
static const unsigned SSTable[] = { ~0, 0, 1, ~0, 2, ~0, ~0, ~0, 3 };
unsigned SS = SSTable[Scale.getImmedValue()];
if (BaseReg.getReg() == 0) {
// Handle the SIB byte for the case where there is no base. The
// displacement has already been output.
assert(IndexReg.getReg() && "Index register must be specified!");
emitSIBByte(SS, getX86RegNum(IndexReg.getReg()), 5);
} else {
unsigned BaseRegNo = getX86RegNum(BaseReg.getReg());
unsigned IndexRegNo = getX86RegNum(IndexReg.getReg());
emitSIBByte(SS, IndexRegNo, BaseRegNo);
}
// Do we need to output a displacement?
if (Disp.getImmedValue() != 0 || ForceDisp32 || ForceDisp8) {
if (!ForceDisp32 && isDisp8(Disp.getImmedValue()))
emitConstant(Disp.getImmedValue(), 1);
else
emitConstant(Disp.getImmedValue(), 4);
}
}
}
static bool isImmediate(const MachineOperand &MO) {
return MO.getType() == MachineOperand::MO_SignExtendedImmed ||
MO.getType() == MachineOperand::MO_UnextendedImmed;
}
unsigned sizeOfPtr (const MachineInstrDescriptor &Desc) {
switch (Desc.TSFlags & X86II::ArgMask) {
case X86II::Arg8: return 1;
case X86II::Arg16: return 2;
case X86II::Arg32: return 4;
case X86II::Arg64: return 8;
case X86II::Arg80: return 10;
case X86II::Arg128: return 16;
default: assert(0 && "Memory size not set!");
}
}
void Emitter::emitInstruction(MachineInstr &MI) {
unsigned Opcode = MI.getOpcode();
const MachineInstrDescriptor &Desc = II.get(Opcode);
// Emit instruction prefixes if neccesary
if (Desc.TSFlags & X86II::OpSize) MCE.emitByte(0x66);// Operand size...
if (Desc.TSFlags & X86II::TB) MCE.emitByte(0x0F);// Two-byte opcode prefix
unsigned char BaseOpcode = II.getBaseOpcodeFor(Opcode);
switch (Desc.TSFlags & X86II::FormMask) {
case X86II::RawFrm:
MCE.emitByte(BaseOpcode);
if (MI.getNumOperands() == 1) {
assert(MI.getOperand(0).getType() == MachineOperand::MO_PCRelativeDisp);
MCE.emitPCRelativeDisp(MI.getOperand(0).getVRegValue());
}
break;
case X86II::AddRegFrm:
MCE.emitByte(BaseOpcode + getX86RegNum(MI.getOperand(0).getReg()));
if (MI.getNumOperands() == 2) {
unsigned Size = sizeOfPtr(Desc);
if (Value *V = MI.getOperand(1).getVRegValueOrNull()) {
assert(Size == 4 && "Don't know how to emit non-pointer values!");
MCE.emitGlobalAddress(cast<GlobalValue>(V));
} else {
emitConstant(MI.getOperand(1).getImmedValue(), Size);
}
}
break;
case X86II::MRMDestReg:
MCE.emitByte(BaseOpcode);
emitRegModRMByte(MI.getOperand(0).getReg(),
getX86RegNum(MI.getOperand(MI.getNumOperands()-1).getReg()));
break;
case X86II::MRMDestMem:
MCE.emitByte(BaseOpcode);
emitMemModRMByte(MI, 0, getX86RegNum(MI.getOperand(4).getReg()));
break;
case X86II::MRMSrcReg:
MCE.emitByte(BaseOpcode);
emitRegModRMByte(MI.getOperand(MI.getNumOperands()-1).getReg(),
getX86RegNum(MI.getOperand(0).getReg()));
break;
case X86II::MRMSrcMem:
MCE.emitByte(BaseOpcode);
emitMemModRMByte(MI, MI.getNumOperands()-4,
getX86RegNum(MI.getOperand(0).getReg()));
break;
case X86II::MRMS0r: case X86II::MRMS1r:
case X86II::MRMS2r: case X86II::MRMS3r:
case X86II::MRMS4r: case X86II::MRMS5r:
case X86II::MRMS6r: case X86II::MRMS7r:
MCE.emitByte(BaseOpcode);
emitRegModRMByte(MI.getOperand(0).getReg(),
(Desc.TSFlags & X86II::FormMask)-X86II::MRMS0r);
if (isImmediate(MI.getOperand(MI.getNumOperands()-1))) {
unsigned Size = sizeOfPtr(Desc);
emitConstant(MI.getOperand(MI.getNumOperands()-1).getImmedValue(), Size);
}
break;
}
}